This invention relates to plastic bags characterized by a draw tape which, when pulled, causes the bag mouth to constrict to a substantially closed condition. Plastic bags of the type described are typically comprised of a bag body folded at the bottom to form front and rear sheets which are ordinarily sealed at the side edges. The upper edges of the front and rear sheets, located opposite the bottom fold, define the mouth of the bag. An upper margin at the bag mouth is typically folded inside the bag to form a hem which is ordinarily sealed to the bag body to form a channel for accommodating the draw tape. Pulling accessible portions of the draw tape typically causes the bag mouth to constrict and close as previously described.
Draw tape bags of the type described are often manufactured by automatic bag making machinery at a relatively rapid rate. This is typically accomplished by passing a web of plastic material through a number of folding, sealing and operating stations. As such, the aforementioned hem is typically made and sealed automatically by machine at a so-called hem sealing station. In many such bag making operations this hem is intermittently sealed to the bag body; that is, the hem is attached to the bag body at spaced intervals, rather than attached to the bag body along its entire girth. Heretofore, such an intermittent hem seal has been ordinarily accomplished by briefly stopping the movement of the web so that a press can be brought into position to heat seal the hem to the bag body at spaced intervals.
Though the intermittent hem seal provided by such an operation has been acceptable, the time required to stop the movement of the web while the press is moved into position to make the seal, however brief it may be, is undesirable. Indeed, almost any stoppage of the web as it proceeds through the manufacturing process may have concomitant drawbacks in efficiency, speed and economy.
Accordingly, it is a primary object of this invention to enable hem seals to be continuously made during the manufacture of draw tape bags. It is another object of this invention to provide an apparatus and method in the manufacture of draw tape bags which enables the creation of an intermittent hem seal without stopping the manufacturing process. Other objects of the invention, along with many features and advantages, will become apparent upon reading the detailed description in conjunction with the accompanying drawings.